Engine trouble - various issues
Posted: Sun Sep 03, 2017 4:50 pm
Hello guys and girls
The time has come to try and sort out some issues with my coupe, if you wouldn't mind helping me diagnose the causes as I'm far from an expert when it comes to engines but I do know my way around a tool kit.
I have a gen 3.5, 2.7 v6, 55plate.
I will include all problems in this thread just incase they are linked and possibly help with diagnosis. However if we concentrate on problems 1-3 first so we don't get confused with crossed information.
I apologize for the long post, just want to get as much information in as possible.
The problems.
1. Intermittent stall/drop in revs on start up. For instance I can jump in the car, start it up fine, runs fine, go to petrol station, get back in and bang, trouble starting. Sometimes it doesn't start and struggles, it turns over but takes time to fire, but always fires, it has never failed to fire up. Once it fires it can be fine and runs smooth, other times revs drop to about 500rpm and feels like it will stall, other times it will stall. So very inconsistent and erratic in behaviour. I do have a video of starting and revs dropping
https://youtu.be/4fLfWtdoa6I
2. When idle, revs drop for a second then back up. (This may have 5min intervals, 30 seconds, 2 min, 3min etc. It can happen a lot or not at all, very irregular on timing for this issue)(I do feel this is probably linked to problem 1)
3. When pulling away engine seems to shake/revs drop when I wouldn't expect it to, I've tried plenty of revs and still seems to be there. Again intermittent sometimes it happens other times it doesn't (Again I feel this maybe linked to problem 1+2)
4. When accelerating hard in 2nd and 3rd gear between 1000rpm and 3400rpm, the engine seems to pull back. So engine accelerates for 1 sec, pulls back 1 sec, accelerates 1 sec, pulls back 1 sec etc making the car kangaroo up the road until I reach 3400rpm, at which point the pull backs stop and car takes off as normal. Once the car has run for 5 mins or so this seems to ease off and eventually disappear. Also seems to happen more in the mornings so maybe the cold is affecting it. This problem is intermittent and doesn't always occur.
5. Car seems down on power between idle rpm and 3400 rpm. Mostly noticeable in 2nd and 3rd gear. It's not terribly slow, but at 3400 rpm it's like a turbo kicks in and bang the car seems to pull with a lot more grunt. This issue is there all the time and is the only issue that is not intermittent (Possibly related to issue 4)
Ok so those are the issues I face.
No engine light has ever come up to say there is an issue, but something is not right for sure.
What I have done so far.
New maf sensor (no change noticed)
Clean iacv and new gasket(I did have a problem with idle rpms jumping around quite a lot, found gasket cracked, this issue has gone now and rpm is consistent, except for the issues as above)
Throttle body cleaned (no change noticed)
New fuel filters(no change noticed, although things do seem smoother(placebo?probably))
Induction kit fitted as old intake pipe had a big crack (no change noticed regarding above issues, it did at the time make the engine feel better and run smoother but issues still persisted)
New brd poly rear engine mount(old was gone, thought this might relate to issue 3, however no change notice)
New spark plugs and HTC leads are on order however I don't feel this is going to make a difference as service manual say plugs were changed not so long a go.
Car has a full service history so oil and filters and such should have all been changed regularly.
Engine itself, to me, sounds fine, pulls well, no weird noises, sounds smooth. Slight tap noise from injectors but that is common as far as I know. Had a family friend who is a mechanic listen while he was at the house and he said engine sounds good. So as far as im concerned the engine is good and solid.
I don't feel the problems are mechanical as such. But more than likely a sensor or communication issue.
I'd prefer to fix this myself as I'm good mechanically, just engines aren't my usual subject matter. Plus garage prices can get ridiculous for time spent troubleshooting issues.
As i say I'm no expert so any help you guys can offer is much appreciated.
Thanks guys
The time has come to try and sort out some issues with my coupe, if you wouldn't mind helping me diagnose the causes as I'm far from an expert when it comes to engines but I do know my way around a tool kit.
I have a gen 3.5, 2.7 v6, 55plate.
I will include all problems in this thread just incase they are linked and possibly help with diagnosis. However if we concentrate on problems 1-3 first so we don't get confused with crossed information.
I apologize for the long post, just want to get as much information in as possible.
The problems.
1. Intermittent stall/drop in revs on start up. For instance I can jump in the car, start it up fine, runs fine, go to petrol station, get back in and bang, trouble starting. Sometimes it doesn't start and struggles, it turns over but takes time to fire, but always fires, it has never failed to fire up. Once it fires it can be fine and runs smooth, other times revs drop to about 500rpm and feels like it will stall, other times it will stall. So very inconsistent and erratic in behaviour. I do have a video of starting and revs dropping
https://youtu.be/4fLfWtdoa6I
2. When idle, revs drop for a second then back up. (This may have 5min intervals, 30 seconds, 2 min, 3min etc. It can happen a lot or not at all, very irregular on timing for this issue)(I do feel this is probably linked to problem 1)
3. When pulling away engine seems to shake/revs drop when I wouldn't expect it to, I've tried plenty of revs and still seems to be there. Again intermittent sometimes it happens other times it doesn't (Again I feel this maybe linked to problem 1+2)
4. When accelerating hard in 2nd and 3rd gear between 1000rpm and 3400rpm, the engine seems to pull back. So engine accelerates for 1 sec, pulls back 1 sec, accelerates 1 sec, pulls back 1 sec etc making the car kangaroo up the road until I reach 3400rpm, at which point the pull backs stop and car takes off as normal. Once the car has run for 5 mins or so this seems to ease off and eventually disappear. Also seems to happen more in the mornings so maybe the cold is affecting it. This problem is intermittent and doesn't always occur.
5. Car seems down on power between idle rpm and 3400 rpm. Mostly noticeable in 2nd and 3rd gear. It's not terribly slow, but at 3400 rpm it's like a turbo kicks in and bang the car seems to pull with a lot more grunt. This issue is there all the time and is the only issue that is not intermittent (Possibly related to issue 4)
Ok so those are the issues I face.
No engine light has ever come up to say there is an issue, but something is not right for sure.
What I have done so far.
New maf sensor (no change noticed)
Clean iacv and new gasket(I did have a problem with idle rpms jumping around quite a lot, found gasket cracked, this issue has gone now and rpm is consistent, except for the issues as above)
Throttle body cleaned (no change noticed)
New fuel filters(no change noticed, although things do seem smoother(placebo?probably))
Induction kit fitted as old intake pipe had a big crack (no change noticed regarding above issues, it did at the time make the engine feel better and run smoother but issues still persisted)
New brd poly rear engine mount(old was gone, thought this might relate to issue 3, however no change notice)
New spark plugs and HTC leads are on order however I don't feel this is going to make a difference as service manual say plugs were changed not so long a go.
Car has a full service history so oil and filters and such should have all been changed regularly.
Engine itself, to me, sounds fine, pulls well, no weird noises, sounds smooth. Slight tap noise from injectors but that is common as far as I know. Had a family friend who is a mechanic listen while he was at the house and he said engine sounds good. So as far as im concerned the engine is good and solid.
I don't feel the problems are mechanical as such. But more than likely a sensor or communication issue.
I'd prefer to fix this myself as I'm good mechanically, just engines aren't my usual subject matter. Plus garage prices can get ridiculous for time spent troubleshooting issues.
As i say I'm no expert so any help you guys can offer is much appreciated.
Thanks guys